This invention relates generally to applying liquid to a region of an object such as the flap of an envelope or the like, in which relative movement brings the object and a liquid applicator adjacent each other. More particularly, the invention relates to controlling the position of a liquid applicator outlet for rapid application of liquid to envelope flaps moved at high speed past the liquid applicator outlet. The invention has particular application to moistening of gummed envelope flaps in a high speed mailing machine.
U.S. Pat. No. 3,911,862 discloses a moistening system for envelope flaps.
Co-pending U.S. Pat. Nos. 5,020,473 and 4,924,804, both filed on Dec. 28, 1988, disclose the high speed moistening of envelope flaps in which the edge of the envelope flap is sensed a given distance upstream of a spray nozzle, the velocity of the envelope is determined, and movement of the nozzle is controlled as a function of the given distance, the sensed flap edge and the envelope velocity. The inventor and assignee in both of those applications are the same as herein, and the disclosures of those two applications are incorporated herein by reference.